It has long been conventional in the construction of exterior walls to utilize as a substrate a gypsum sheathing having treated paper adhered to the opposite surfaces thereof. The normal procedure has been to adhere an insulation layer to one of the paper faces of the gypsum substrate, and then an outer finish layer or coat is applied to the insulation layer to complete the assembly. Although this type of wall construction has generally proven to be satisfactory, water penetration may cause deterioration of the treated paper on the gypsum substrate, causing this to separate from the gypsum sheathing, hence adversely affecting wall integrity.
In an effort to improve wall integrity, a fiberglass mat has been adhered to the surface of the gypsum core in lieu of the conventional treated paper. However, it has been found that moisture penetration may still result in deterioration of the bond between the fiberglass and the gypsum core and may result in separation of the same from the gypsum core. The fiberglass has also been found to be subject to alkali attack as a result of the adhesive, resulting in deterioration and separation of the fiberglass from the gypsum core.
Another attempt at improving wall integrity is illustrated in U.S. Pat. No. 4,882,888. This patent discloses the coating of the fiberglass-faced gypsum with a water-based, water-resistant coating, such as water-based acrylic coating, prior to the application of any adhesive thereto, to form a barrier against excessive moisture penetration. This system may serve to limit water penetration but does not prevent deterioration once penetration does eventually occur.
The object of the present invention is to overcome the shortcomings of the aforementioned prior art. Another object of the instant invention is to eliminate deterioration of the substrate due to water penetration. An additional object of the present invention is to provide for the removal of water which does penetrate this system. Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds in connection with the accompanying illustrative drawings .